Generally, the operation of a robot or a mechanical apparatus implementing a specific operation is controlled through an actuator directly attached to a joint of an operation implementing part. When driving the mechanical apparatus with the actuator directly attached to the joint of the operation implementing part, the weight and volume of the operation implementing part inevitably increase, thereby making it difficult to achieve a reduction in the size of the mechanical apparatus.
Further, a robot arm of a surgical robot is constructed to perform operations, such as tissue incision or suture, in the body in a limited space. Thus, a robot arm for surgery is limited in size. In a robot arm of a general surgical robot, an actuator is provided to a front end of the robot arm, where joint parts and surgical instruments are mounted, to allow the robot arm to operate at a surgical site. Thus, it is necessary to limit the number of actuators mounted on the robot arm in order to reduce the volume of the robot arm to be inserted into the body. As a result, in order for a general robot arm to move to a position close to tissue to be surgically operated, several sites of the skin 1 are incised and an operation is performed through the incised skin sites, as illustrated in FIG. 1a. Such robot arms r1 and r2 require many skin incisions whose positions are dependent upon the objective of surgery, so that several scars remain on the surgical sites, leaving an unattractive appearance. Particularly, in the case where the surgical sites are likely to be exposed in daily life, unattractive appearance becomes a more serious problem. Additionally, since the actuators increase the weight of the robot arms r1, r2, there is a problem in that a load applied to the robot arms r1, r2 is increased. Moreover, since the robot arms r1, r2 are mounted on different positions, the number of robot arm stands for regulating the positions of the robot arm r1, r2 also increases, and as a result, the installation space becomes small, which makes it difficult to perform a surgical operation.
In view of the above problems, Korean Patent Publication No. 2009-0124552A proposes a robot arm illustrated in FIG. 1b. The robot arm includes a plurality of nodes 20, elastic members 16 connecting the adjacent nodes 20 to constitute joints, and joint driving wires 12, 14 penetrating the nodes 20. Drawing of the joint driving wires 12, 14 leads to contraction or stretching of the elastic members 16 to bend the joints.
In this case, however, since the joint driving wires 12, 14 are connected to each other through the elastic members 16 and the nodes 20, there is a problem that a wire-type drive unit including the joint driving wires 12, 14 is easily damaged when an operation implementing part is replaced with a new one upon operational failure of a mechanical apparatus. Another problem is that the wire-type drive unit has a low strength to allow only an excessively limited load to be applied to an operation part 30. Furthermore, since the joint driving wires 12, 14 control the operation of joint parts of the robot arm as well as a surgical instrument 30, only a limited number of the driving wires 12, 14 can be mounted to control the joints in the robot arm having an extremely limited volume, causing a problem that several sites are incised to allow the robot arm to approach a surgical target, as in existing robot arms. Moreover, a load applied to the robot arm increases with increasing length of the robot arm so that the robot arm undergoes vibration by the load during operation of the surgical instrument 30. This makes it difficult to achieve precise control of the robot arm.